It's actually an older 135 gallon (used to be a standard size from All Glass, Perfecto, and Oceanic). A standard 125 is 72 x 18 x 23 and is made with thinner glass. Aquarium sizes are often based on outside dimensions (displacement) not net volume. Which is why you see them labeled as "Size 125" and not "125 Gallon" on the labels.
Because there was such little difference in dimension but a big difference in price 135's have been discontinued by all brands some time ago due to poor sales.
Zigman is right though, Take an inch off each dimension and you will be relatively close to the net volume.
Andy
P.S. If I could see the frame I could tell you which brand it is but it's covered by the stand in the photos. The tank with the white cabinet next to it is an Oceanic Washed Oak setup though.